/*
 *   This program is free software: you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation, either version 3 of the License, or
 *   (at your option) any later version.
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU General Public License for more details.
 *
 *   You should have received a copy of the GNU General Public License
 *   along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

/*
 * SimpleBatchFilter.java
 * Copyright (C) 2005-2012 University of Waikato, Hamilton, New Zealand
 *
 */

package weka.filters;

import weka.core.Instance;
import weka.core.Instances;

/**
 * This filter is a superclass for simple batch filters.
 * <p/>
 * 
 * <b>General notes:</b><br/>
 * <ul>
 * <li>After adding instances to the filter via input(Instance) one always has
 * to call batchFinished() to make them available via output().</li>
 * <li>After the first call of batchFinished() the field m_FirstBatchDone is set
 * to <code>true</code>.</li>
 * </ul>
 * <p/>
 * 
 * <b>Example:</b><br/>
 * The following code snippet uses the filter <code>SomeFilter</code> on a
 * dataset that is loaded from <code>filename</code>.
 * 
 * <pre>
 * import weka.core.*;
 * import weka.filters.*;
 * import java.io.*;
 * ...
 * SomeFilter filter = new SomeFilter();
 * // set necessary options for the filter
 * Instances data = new Instances(
 *                    new BufferedReader(
 *                      new FileReader(filename)));
 * Instances filteredData = Filter.useFilter(data, filter);
 * </pre>
 * 
 * <b>Implementation:</b><br/>
 * Only the following abstract methods need to be implemented:
 * <ul>
 * <li>globalInfo()</li>
 * <li>determineOutputFormat(Instances)</li>
 * <li>process(Instances)</li>
 * </ul>
 * <br/>
 * And the <b>getCapabilities()</b> method must return what kind of attributes
 * and classes the filter can handle.
 * <p/>
 * 
 * If more options are necessary, then the following methods need to be
 * overriden:
 * <ul>
 * <li>listOptions()</li>
 * <li>setOptions(String[])</li>
 * <li>getOptions()</li>
 * </ul>
 * <p/>
 * 
 * To make the filter available from commandline one must add the following main
 * method for correct execution (&lt;Filtername&gt; must be replaced with the
 * actual filter classname):
 * 
 * <pre>
 *  public static void main(String[] args) {
 *    runFilter(new &lt;Filtername&gt;(), args);
 *  }
 * </pre>
 * <p/>
 * 
 * <b>Example implementation:</b><br/>
 * 
 * <pre>
 * import weka.core.*;
 * import weka.core.Capabilities.*;
 * import weka.filters.*;
 * 
 * public class SimpleBatch extends SimpleBatchFilter {
 * 
 *     public String globalInfo() {
 *         return &quot;A simple batch filter that adds an additional attribute 'bla' at the end containing the index of the processed instance.&quot;;
 *     }
 * 
 *     public Capabilities getCapabilities() {
 *         Capabilities result = super.getCapabilities();
 *         result.enableAllAttributes();
 *         result.enableAllClasses();
 *         result.enable(Capability.NO_CLASS); // filter doesn't need class to be set
 *         return result;
 *     }
 * 
 *     protected Instances determineOutputFormat(Instances inputFormat) {
 *         Instances result = new Instances(inputFormat, 0);
 *         result.insertAttributeAt(new Attribute(&quot;bla&quot;), result.numAttributes());
 *         return result;
 *     }
 * 
 *     protected Instances process(Instances inst) {
 *         Instances result = new Instances(determineOutputFormat(inst), 0);
 *         for (int i = 0; i &lt; inst.numInstances(); i++) {
 *             double[] values = new double[result.numAttributes()];
 *             for (int n = 0; n &lt; inst.numAttributes(); n++)
 *                 values[n] = inst.instance(i).value(n);
 *             values[values.length - 1] = i;
 *             result.add(new DenseInstance(1, values));
 *         }
 *         return result;
 *     }
 * 
 *     public static void main(String[] args) {
 *         runFilter(new SimpleBatch(), args);
 *     }
 * }
 * 
 * </pre>
 * <p/>
 * 
 * <b>Options:</b><br/>
 * Valid filter-specific options are:
 * <p/>
 * 
 * -D <br/>
 * Turns on output of debugging information.
 * <p/>
 * 
 * @author FracPete (fracpete at waikato dot ac dot nz)
 * @version $Revision$
 * @see SimpleStreamFilter
 * @see #input(Instance)
 * @see #batchFinished()
 * @see #m_FirstBatchDone
 */
public abstract class SimpleBatchFilter extends SimpleFilter {

    /** for serialization */
    private static final long serialVersionUID = 8102908673378055114L;

    /**
     * returns true if the output format is immediately available after the input
     * format has been set and not only after all the data has been seen (see
     * batchFinished())
     * 
     * @return true if the output format is immediately available
     * @see #batchFinished()
     * @see #setInputFormat(Instances)
     */
    @Override
    protected boolean hasImmediateOutputFormat() {
        return false;
    }

    /**
     * Returns whether to allow the determineOutputFormat(Instances) method access
     * to the full dataset rather than just the header.
     * <p/>
     * Default implementation returns false.
     * 
     * @return whether determineOutputFormat has access to the full input dataset
     */
    public boolean allowAccessToFullInputFormat() {
        return false;
    }

    /**
     * Input an instance for filtering. Filter requires all training instances be
     * read before producing output (calling the method batchFinished() makes the
     * data available). If this instance is part of a new batch, m_NewBatch is set
     * to false.
     * 
     * @param instance the input instance
     * @return true if the filtered instance may now be collected with output().
     * @throws IllegalStateException if no input structure has been defined
     * @throws Exception             if something goes wrong
     * @see #batchFinished()
     */
    @Override
    public boolean input(Instance instance) throws Exception {
        if (getInputFormat() == null) {
            throw new IllegalStateException("No input instance format defined");
        }

        if (m_NewBatch) {
            resetQueue();
            m_NewBatch = false;
        }

        bufferInput(instance); // bufferInput() makes a copy of the instance.

        if (isFirstBatchDone()) {
            Instances inst = new Instances(getInputFormat());
            inst = process(inst);
            for (int i = 0; i < inst.numInstances(); i++) {
                push(inst.instance(i), false); // No need to copy instance
            }
            flushInput();
        }

        return m_FirstBatchDone;
    }

    /**
     * A version of the input(Instance) method that enables input of a whole dataset
     * represented as an Instances object into the filter. This method is more
     * efficient when processing batches other than the first batch of data because
     * it can apply the process(Instances) method to the full batch and does not
     * have to process individual instances independently.
     *
     * @param instances the input instances
     * @return true if the filtered instances may now be collected with output().
     * @throws IllegalStateException if no input structure has been defined
     * @throws Exception             if something goes wrong
     * @see #batchFinished()
     */
    public boolean input(Instances instances) throws Exception {
        if (getInputFormat() == null) {
            throw new IllegalStateException("No input instance format defined");
        }

        if (m_NewBatch) {
            resetQueue();
            m_NewBatch = false;
        }

        for (Instance instance : instances) {
            bufferInput(instance); // bufferInput() makes a copy of the instance.
        }

        if (isFirstBatchDone()) {
            Instances inst = new Instances(getInputFormat());
            inst = process(inst);
            for (int i = 0; i < inst.numInstances(); i++) {
                push(inst.instance(i), false); // No need to copy instance
            }
            flushInput();
        }

        return m_FirstBatchDone;
    }

    /**
     * Signify that this batch of input to the filter is finished. If the filter
     * requires all instances prior to filtering, output() may now be called to
     * retrieve the filtered instances. Any subsequent instances filtered should be
     * filtered based on setting obtained from the first batch (unless the
     * setInputFormat has been re-assigned or new options have been set). Sets
     * m_FirstBatchDone and m_NewBatch to true.
     * 
     * @return true if there are instances pending output
     * @throws IllegalStateException if no input format has been set.
     * @throws Exception             if something goes wrong
     * @see #m_NewBatch
     * @see #m_FirstBatchDone
     */
    @Override
    public boolean batchFinished() throws Exception {
        int i;
        Instances inst;

        if (getInputFormat() == null) {
            throw new IllegalStateException("No input instance format defined");
        }

        // get data
        inst = new Instances(getInputFormat());

        // if output format hasn't been set yet, do it now
        if (!hasImmediateOutputFormat() && !isFirstBatchDone()) {
            if (allowAccessToFullInputFormat()) {
                setOutputFormat(determineOutputFormat(inst));
            } else {
                setOutputFormat(determineOutputFormat(new Instances(inst, 0)));
            }
        }

        // don't do anything in case there are no instances pending.
        // in case of second batch, they may have already been processed
        // directly by the input method and added to the output queue
        if (inst.numInstances() > 0) {
            // process data
            inst = process(inst);

            // clear input queue
            flushInput();

            // move it to the output
            for (i = 0; i < inst.numInstances(); i++) {
                push(inst.instance(i), false); // No need to copy instance
            }
        }

        m_NewBatch = true;
        m_FirstBatchDone = true;

        return (numPendingOutput() != 0);
    }
}
